The Zika virus may trigger an immune response that causes developing brain cells to stop dividing and self-destruct.

The link between Zika infection and the birth of babies with abnormally small heads, or microcephaly, has grown stronger, but it is still not clear how the virus attacks developing brains. Tariq Rana at the University of California, San Diego, and his team grew cerebral organoids — 3D structures that model the developing brain — from human embryonic stem cells and then infected them with Zika. Over a 5-day period, uninfected organoids grew by 22.6%, whereas those exposed to Zika shrank by 16%.

Zika infection boosted the activity of a pathogen-sensing gene, TLR3, which has been linked to brain inflammation and degeneration. Blocking the TLR3 protein in infected organoids lessened the damage caused by the virus.

Cell Stem Cell (2016)